It would depend upon how serious their injuries were where they were treated. Some would have been treated locally in Egypt, some would have been transferred to hospitals in India or South Africa or Kenya. Others would have been returned to the UK for further recuperation or recovery, or for discharge. There is no reason that they would necessarily been returned to London, unless they were actually from London, and if so, they would be as subject to bombing as any other resident of London. Of course, as most cities in the UK were subject to bombing, they could have been involved in bombing if they weren't from London.